LX-1031 is a potent, orally available tryptophan 5-hydroxylase (TPH) inhibitor that reduces serotonin (5-HT) synthesis peripherally.In Vivo: With oral administration of LX-1031 in mice, the average 5-HT reductions in the jejunum relative to control are appr 33, 51, and 66% with the 15, 45 and 135 mg/kg/day doses respectively. In a preliminary report, the effects of LX-1031, 100 mg/kg daily, on 5-HT levels in jejunal mucosa are reversible within 2 days of discontinuation in mice[1]. LX-1031 dose-dependently reduces expression of 5-HT in the duodenum, jejunum and ileum, but has no effect on brain 5-HT levels in preclinical assay[2].